In the field of industrial hydraulic and pneumatic equipment, a mechanical valve is often employed to selectively open or close a hydraulic or pneumatic pathway or channel within the equipment. Typically, the valve is operated by way of a solenoid. In general, a solenoid includes a coiled conductor forming a cylinder, and a metallic core located within the cylinder. When the coil is energized by way of an electrical voltage, current flows through the coiled conductor, creating a magnetic field within the cylinder that induces a moving force upon the core along the long axis of the cylinder. When the energizing voltage is removed, the magnetic field is eliminated, and the related force on the core ceases.
When used in conjunction with a valve, the core may be attached to a portion of the valve, while the core is mechanically biased by a spring against a first mechanical “stop,” or limit, so that the valve will remain in a first position, associated with either a closed or open state of the valve, when the solenoid is not energized. When a voltage is applied to the solenoid, the core moves to counteract the force of the spring, thereby changing the position of the valve to a second position defined by a second mechanical stop, thereby opening or closing the valve. In some applications, two or more solenoids may be employed in cooperation to open and close an associated valve.
In some hydraulic and pneumatic equipment, the valve directly acted upon by the solenoid is the primary valve of concern, termed a “direct acting valve.” More typically, however, the valve acted upon by the solenoid is a “pilot valve,” which allows air or liquid to pressurize a second, main valve, which then operates to force the main valve into an open or closed state.
Some solenoids are designed to be energized by a DC voltage, while others are operated via an AC voltage, depending on the particular application in which the valve is utilized. For example, some valve applications may require solenoids that accept a voltage of −24 volts DC (VDC), while others may employ solenoids that are properly energized with a line voltage of 115 volts AC (VAC) root-mean-square (RMS). Thus, a hydraulic and pneumatic equipment manufacturer may offer a range of versions of a particular valve product, with each version employing a different solenoid reactive to a particular AC or DC voltage. In so doing, the manufacturer's costs are often increased by designing, manufacturing and stocking multiple versions of valve products employing different solenoids.
Further, distribution of the voltage to the solenoid is often accomplished by way of an electrical connector or terminal strip and a printed circuit board (PCB). As a result, safety requirements, such as those specified by Underwriters Laboratories® and other safety testing organizations, necessitate larger wires or circuit traces, as well as greater spacing between traces or connection points, for larger AC voltages, such as 115 VAC, when compared to those required for smaller DC voltages, such as −24 VDC. These larger conductors and spacing typically increase the size of the PCBs and connectors, or mandate the use of the larger terminal strips, thus increasing the overall size of the valve product, and often rendering the product less desirable and more expensive to the customer.